The core gameplay is copy-pasted from one of the greatest video games of all times, Sacrifice by Shiny. You have up to two sides fighting with each other for control of mana- I mean, FAN fountains to destroy your oponent's Altar- I mean the SCENE. Your small armies are controlled via simple commands and supported by your main hero with spells- I mean the SOLOS. It's a great concept really, and Sacrifice pulled it off perectly, of course.
The problem with Brutal Legend is that the devs had not a slightest idea how to build this kind of game. That's probably the reason they decided to cover it up with tons of autistic non-content, but I will get to that in a minute.
The core gameplay is over-simplified and absurdly unbalanced. You don't have to do any real resource management (your fans are generating only from the fan booths, there are no real base mana units) and from a variety of units, only few are relevant (among all three armies). And even they don't matter, since you have absolutely overpowered guitar solos who can destroy everything around you after a short QTE. It's decent enough for a few fights, but after you discover that the best way is to bait all your enemies into one spot and cast one AoE attack which will take all of them, there's suddenly no challenge, even vs the highest difficulty level. The multiplayer is dead anyway.
But all of above is just a small fraction of the whole game. There are up to 8 (?) stage battles throughout the whole game, which is laughable. The rest of the game consists of autism in an open world area, searching for throphies and doing lazy side-quests, while struggling with hell of a driving model. There's nothing to add about this part of the game, but at the same time it makes up to 90% of it.
The theme is amazing, but if you want to listen to some music, just open up your Internet browser. If it's this kind of core gameplay you're looking for, just play Sacrifice. This game is not worth it, unfortunately.